There are known piperazine compounds of the formula ##STR2## where R.sub.2 is hydrogen or a chlorine atom in the 2-position and R.sub.1 is a lower alkyl group, a phenyl radical, a benzyl radical or a chlorophenyl radical when Y is a single bond between the piperazine ring and the phenyl group, or where R.sub.1 is a lower alkyl group, a phenyl radical a benzyl radical a chlorophenyl radical or a methoxyphenyl radical when Y is methylene, dimethylene, trimethylene, or the group --CH.sub.2 --CH.dbd.CH. Several of these compounds, especially those where Y is the group --CH.sub.2 --CH.dbd.CH-- have proven to be analgetically active (J. Med. Chem. Volume 11, page 803 (1968)).
Furthermore, there are known piperazine compounds of the following formula ##STR3## In this formula A, for example, stands for the group --CH.sub.2 --CH.sub.2 --CO-- and R is a 2-chlorophenyl radical a 2-methylphenyl radical or a pyridyl-(2) radical These compounds were examined as to whether they had a suppressing action on the central nervous system (sedative and atactive actions; tranquillizing action). Several of the compounds showed activity (J. Med. Chem. Volume 12, page 867 (1969)).
Finally, there are described in German OS No. 2623772 piperazine derivatives of the general formula ##STR4## in which R is a low molecular weight straight or branched chain alkyl group having 1 to 6 carbon atoms, a low molecular weight, straight or branched chain alkenyl group having 2 to 5 carbon atoms, a cycloalkyl group having 3 to 6 carbon atoms, a low molecular weight, straight or branched chain alkyl group having 1 to 6 carbon atoms which is joined to a low molecular weight, straight or branched chain alkoxy group having 1 to 6 carbon atoms or a hydroxy group, a low molecular weight, straight or branched chain alkenyl group having 2 to 5 carbon atoms which is joined to a low molecular weight, straight or branched chain alkoxy group having 1 to 6 carbon atoms, or a tetrahydrofuryl group; R.sub.1 and R.sub.2, which can be the same or different are hydrogen or low molecular weight, straight or branched chain alkyl groups having 1 to 4 carbon atoms (with the proviso that both groups R.sub.1 and R.sub.2 cannot be a hydrogen atom); and R.sub.3 is a hydrogen atom, a halogen atom, a low molecular weight, straight or branched chain alkyl group having 1 to 4 carbon atoms, a low moleclar weight, straight or branched chain alkoxy group having 1 to 4 carbon atoms or a hydroxy group.
These compounds are stated to have an analgetic action, in which case however, it is a matter of peripherally active materials. In contrast the compounds of the invention are centrally active analgetics.